Spring Boot MCQ Questions – Page 14 of 49

Q: What is the HTTP status code and 'X-Custom-Header' value returned by this Spring Boot controller method?

A) Status: 200 OK, X-Custom-Header: "MyValue". The constructor `new ResponseEntity<>(body, headers, HttpStatus)` allows specifying custom HTTP headers along with the body and status. The 'X-Custom-Header' is correctly added and returned.

Q: If the `run` method of `AppRunner` is executed, what will be the outcome?

B) A `NullPointerException` when `new NonSpringManagedClass().performAction()` is called.. `NonSpringManagedClass` is not a Spring-managed component (it lacks `@Component`, `@Service`, etc.). Therefore, Spring's `@Autowired` mechanism will completely ignore the annotation on `myRepo`, leaving the field `null`. Accessing `myRepo.getData()` will then result in a `NullPointerException`.

Q: What error will occur when this Spring Boot application starts if `spring-boot-starter-data-jpa` is missing from the classpath?

A) A `ClassNotFoundException` related to JPA classes (e.g., `EntityManagerFactory`).. When `spring-boot-starter-data-jpa` is missing, the necessary JPA auto-configurations and core JPA classes (like `EntityManagerFactory`) are not available. Spring Boot will attempt to configure JPA features because it finds `JpaRepository` interfaces, but will eventually encounter a `ClassNotFoundException` when trying to load required JPA infrastructure classes.

Q: Consider the following Spring Boot code. What error will it produce upon compilation?

B) A compile-time error due to incompatible types: `Integer` cannot be converted to `String` for the `ResponseEntity` body.. The method `getNumericalData` is declared to return `ResponseEntity `, but `ResponseEntity.ok(number)` is attempting to place an `Integer` object into the body. This leads to a compile-time type mismatch.

Q: What is a key difference in usage between `@PathVariable` and `@RequestParam`?

B) `@PathVariable` extracts values from the URI path segments, while `@RequestParam` extracts values from the query string.. `@PathVariable` is used for extracting dynamic parts of the URL itself (e.g., `/users/123`), whereas `@RequestParam` is for parameters passed after the '?' in the URL (e.g., `/users?id=123`).

Q: Given this Spring Boot controller method, what HTTP status code and body will the client receive if a DELETE request targets `/api/orders/789` and the order is successfully removed?

C) HTTP 200 OK, with body "Order cancelled successfully.". The method explicitly returns a `ResponseEntity ` with `HttpStatus.OK` and a specific message, so the client will receive an HTTP 200 OK status code along with the "Order cancelled successfully." message in the response body.

Q: What is the HTTP response body when a GET request is made to `/search/java%20spring`?

A) Searching for: java spring. Spring automatically decodes URL-encoded path variables. The `%20` in the URL is decoded into a space character before being passed to the method parameter.

Q: What is the primary use of the `@ModelAttribute` annotation on a method parameter in a Spring MVC controller for view rendering?

B) To bind request parameters to an object and add that object to the `Model`.. When `@ModelAttribute` is used on a method parameter, Spring binds request parameters to the annotated object and then automatically adds this object to the `Model` under a generated or specified name, making it available to the view.

Q: What error will occur when this Spring Boot application attempts to start?

B) Runtime error: PatternSyntaxException: Unclosed character class.. The regular expression `[a-z}` is malformed due to an unclosed character class. Spring attempts to parse these path variable patterns during application startup, which will result in a `PatternSyntaxException`.

Q: Which of the following statements best describes the primary additional capability that Spring's `ApplicationContext` provides compared to a basic `BeanFactory`?

C) Event publishing, internationalization (i18n), and AOP integration. `ApplicationContext` extends `BeanFactory` and adds enterprise-specific features like message source handling for internationalization, event publishing, and comprehensive AOP integration.

Q261 medium code output

What is the HTTP status code and 'X-Custom-Header' value returned by this Spring Boot controller method?

java

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {
    @GetMapping("/headers")
    public ResponseEntity<String> getWithHeaders() {
        HttpHeaders headers = new HttpHeaders();
        headers.add("X-Custom-Header", "MyValue");
        return new ResponseEntity<>("Data", headers, HttpStatus.OK);
    }
}

Q262 medium code error

If the `run` method of `AppRunner` is executed, what will be the outcome?

java

import org.springframework.stereotype.Repository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Repository class MyRepo { public String getData() { return "Data"; } }

// NOT a Spring managed class
class NonSpringManagedClass {
    @Autowired private MyRepo myRepo; 
    public String performAction() { return myRepo.getData(); }
}

@Component class AppRunner implements CommandLineRunner {
    @Override public void run(String... args) throws Exception {
        new NonSpringManagedClass().performAction(); 
    }
}

Q263 medium code error

What error will occur when this Spring Boot application starts if `spring-boot-starter-data-jpa` is missing from the classpath?

java

package com.example.app;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.SpringApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@SpringBootApplication
public class MissingJpaApp {
    public static void main(String[] args) {
        SpringApplication.run(MissingJpaApp.class, args);
    }
}

@Repository
interface MyEntityRepository extends JpaRepository<Object, Long> {}

Q264 medium code error

Consider the following Spring Boot code. What error will it produce upon compilation?

java

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;

public class ResponseEntityTest {
    public ResponseEntity<String> getNumericalData() {
        Integer number = 42;
        return ResponseEntity.ok(number);
    }
}

Q265 medium

What is a key difference in usage between `@PathVariable` and `@RequestParam`?

Q266 medium code output

Given this Spring Boot controller method, what HTTP status code and body will the client receive if a DELETE request targets `/api/orders/789` and the order is successfully removed?

java

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/orders")
public class OrderController {

    private OrderService orderService;

    // Constructor injected orderService

    @DeleteMapping("/{id}")
    public ResponseEntity<String> cancelOrder(@PathVariable Long id) {
        orderService.cancelOrder(id);
        return new ResponseEntity<>("Order cancelled successfully.", HttpStatus.OK);
    }
}

Q267 medium code output

What is the HTTP response body when a GET request is made to `/search/java%20spring`?

java

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class SearchController {
    @GetMapping("/search/{query}")
    public String performSearch(@PathVariable String query) {
        return "Searching for: " + query;
    }
}

Q268 medium

What is the primary use of the `@ModelAttribute` annotation on a method parameter in a Spring MVC controller for view rendering?

Q269 medium code error

What error will occur when this Spring Boot application attempts to start?

java

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    @GetMapping("/items/{id:[a-z}")
    public String getItemById(@PathVariable String id) {
        return "Item ID: " + id;
    }
}

Q270 medium

Which of the following statements best describes the primary additional capability that Spring's `ApplicationContext` provides compared to a basic `BeanFactory`?

Q271 medium code output

What is the output of this code when `App` is executed?

java

import javax.annotation.PostConstruct;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.annotation.*;
import org.springframework.stereotype.Component;

@Component class MyBean { public MyBean() { System.out.println("1. MyBean Ctor"); } @PostConstruct public void init() { System.out.println("3. MyBean @PostConstruct"); } }
@Component class MyProcessor implements BeanPostProcessor { @Override public Object postProcessBeforeInitialization(Object b, String n) throws BeansException { if (b instanceof MyBean) System.out.println("2. Before Init: " + n); return b; } @Override public Object postProcessAfterInitialization(Object b, String n) throws BeansException { return b; } }
@ComponentScan
public class App { public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App.class); context.close(); } }

Q272 medium code output

What is the output of this code?

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@SpringBootApplication
public class MyApplication {
    static class DataSource {
        private static int instanceCount = 0;
        public DataSource() { instanceCount++; }
        public String getConnectionUrl() { return "jdbc:mysql://localhost/db" + instanceCount; }
    }
    static class MyRepository {
        private final DataSource dataSource;
        public MyRepository(DataSource ds) { this.dataSource = ds; }
        public String getRepositoryInfo() { return "Repo using " + dataSource.getConnectionUrl(); }
    }
    @Bean public DataSource dataSource() { System.out.println("Creating new DataSource instance"); return new DataSource(); }
    @Bean public MyRepository myRepository() { return new MyRepository(dataSource()); } // Spring intercepts
    public static void main(String[] args) {
        MyRepository repository = SpringApplication.run(MyApplication.class, args).getBean(MyRepository.class);
        System.out.println(repository.getRepositoryInfo());
    }
}

Q273 medium code output

Given `application.properties` contains `server.port=8080` and the following Java code, what does it print?

java

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class PortChecker {
    @Value("#{${server.port} > 8000 ? 'High Port' : 'Low Port'}")
    private String portStatus;

    public String getPortStatus() {
        return portStatus;
    }
}
// In a Spring Boot application, if this component is scanned:
// PortChecker checker = applicationContext.getBean(PortChecker.class);
// System.out.println(checker.getPortStatus());

Q274 medium

Which annotation is commonly used in conjunction with `@Service` methods to define transactional boundaries for business operations?

Q275 medium

What is the primary benefit of using `ResponseEntity` in a Spring Boot REST controller instead of simply returning a POJO or String?

Q276 medium code error

What error will occur when the Spring application context attempts to initialize these components?

java

import org.springframework.stereotype.Component;
import org.springframework.beans.factory.annotation.Autowired;

@Component
public class ComponentA {
    private final ComponentB b;
    public ComponentA(ComponentB b) {
        this.b = b;
    }
}

@Component
public class ComponentB {
    private final ComponentA a;
    public ComponentB(ComponentA a) {
        this.a = a;
    }
}

Q277 medium code output

What is the expected outcome (exception) if a POST request with body `{"name":""}` is sent to the following controller, considering the validation annotations?

java

import org.springframework.web.bind.annotation.*;
import jakarta.validation.Valid;
import jakarta.validation.constraints.NotBlank;
import lombok.Data;

@Data
class NameDto {
    @NotBlank(message = "Name cannot be blank")
    private String name;
}

@RestController
@RequestMapping("/names")
public class NameController {

    @PostMapping
    public String submitName(@Valid @RequestBody NameDto nameDto) {
        return "Name submitted: " + nameDto.getName();
    }
}

Q278 medium code error

What error occurs when accessing `/api/data/123` with the following controller?

java

import org.springframework.web.bind.annotation.*;

@RestController
public class DataController {
    @GetMapping("/api/data/{id}")
    public String getData(@RequestParam String id) {
        return "Data ID: " + id;
    }
}

Q279 medium code output

What is the output when '/admin/users' is accessed, considering both local and global handlers?

java

import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;
import org.springframework.http.HttpStatus;

// Assumed: GlobalExceptionHandler.java with @ControllerAdvice exists:
// @ControllerAdvice
// public class GlobalExceptionHandler {
//    @ExceptionHandler(IllegalStateException.class)
//    public ResponseEntity<String> handleGlobalState(IllegalStateException ex) {
//        return new ResponseEntity<>("Global State Error: " + ex.getMessage(), HttpStatus.CONFLICT);
//    }
// }

@RestController
@RequestMapping("/admin")
public class AdminController {
    @GetMapping("/users")
    public String getUsers() {
        throw new IllegalStateException("User session invalid");
    }

    @ExceptionHandler(IllegalStateException.class)
    public ResponseEntity<String> handleLocalState(IllegalStateException ex) {
        return new ResponseEntity<>("Local State Problem: " + ex.getMessage(), HttpStatus.UNAUTHORIZED);
    }
}

Q280 medium code error

What will be the outcome during the Spring Boot application startup?

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
class ServiceA {}

@Component
class ServiceB {}

@Component
class MyConsumer {
    @Autowired
    public MyConsumer(ServiceA serviceA) {}

    @Autowired
    public MyConsumer(ServiceB serviceB) {}
}

🌱 Spring Boot MCQ Questions – Page 14